Motion controlling means for slide rules



July 19, 1949- A. F. ECKEL MOTION CONTROLLNG MEANS FOR SLIDE RULES ZAT/5,442

Filed Aug. 2o, 1947 3 Sheets-Sheet l mwN www

July 19, 1949. A. F. ECKEL 2,475,442

MOTION CONTROLLING MEANS FOR SLIDE RULES Filed Aug. 20, 1947 3 Sheets-Sheet 2 fr; were Zw".- L ri/2 uffi/Ffh# Juy 19, 1949. A F, ECKEL 2,476,442

MOTION CONTROLLING MEANS FOR SLIDE RULES Filed Aug. 20, 1947 3 Sl'xes-Shee?l 5 /30 gy YV mv Patented July 19, l1949 MOTION CONTROLLING MEANS FOR SLIDE RULES Arthur F. Eckel, Evanston, Ill., assgnor to Louise Pickett, La Grange, and Myrtle Eekel, Evanston, Ill.

Application August 20, 1947, Serial No. 769,689

10 Claims. 1

This invention relates to slide rules, and has particularly to do with means for controlling the movements of the slider and cursor thereof.

It is well known that in the use of slide rules time is lost in attempting to adjust the slider in accurate register with the stator, and likewise in adjusting the cursor in register with the slider and stator. Often it is necessary to adjust either of these movable elements to a micrometric degree, but this has been difdcult.

An object of the present invention is, therem fore, the provision of means for enabling the user of a slide rule to produce micrometric movements of the movable elements quickly and to the exact degree desired.

Formerly in the use of slide rules, it has been found that when either the slider or the cursor has been set in a desired position and the other is then moved, the rst one set often becomes dislodged from its set position.

It is, therefore, another object of the present invention to provide means for locking the slider and the cursor in their set positions so that they will not be moved accidentally, but only when the user desires to deliberately move them.

It is a still furtherobject' to provide a novel type of slider for a slide rule which in normal position is locked relative to the stator, and which can be unlocked by the user when it is desired to move the slider.

The slider of the slide rule of the present invention is composed of two longitudinally eX- tending parts having inter-engaging wedge surfaces, and spring means biasing the parts in directions effective for bringing the parts into fricn tion engagement with the respective elements of the stator, thereby locking the slider in place.

Another object is the provision of simple release means for releasing the locking means of the slider so that the user can readily slide the slider.

Still another object of the invention is the pron vision of a novel slider in which the scale pieces thereon are movable to a limited extent along the slidenand this movement is controlled by a means for accomplishing movements of the scale pieces in micrometrie degrees. The slider is moved to the approximate position desired and after this position is established the scale pieces on the slider can be adjusted in extremely line degrees to bring the scale pieces thereon in perfect regisn ter with the scale pieces on the stator.

Still another object is the provision of adjustable stop means on the slider to form limits to Which the scale pieces thereon can be adjusted.

It has also been well known that in the use of previous types of slide rules, the cursor was many times likely to be accidentally moved from its position after the user has once set it.

It is, therefore, another object of the present invention to provide locking means for the cursor which is eiective for securing the cursor in a position after being set, so that it will not be accidentally moved therefrom.

Another object is the provision of a novel locking means for the cursor of a slide rule which can be provided in the cursor and adapted to cooperate with the stator without any special design of the stator elements for this purpose.

A further object is the provision of means for accomplishing micrometric movements of the cursor. The user, when desiring to make such movements, releases the locking means and such movements are made under the immediate attention of the user and at all other times the locking means of the cursor is normally in locking engagement with the slide rule.

Still another object of the invention is the provision of adjustable limit means for limiting the extent of movement of the cursor, this feature being convenient in fixing the point at the end of the rule to which the cursor can be moved so that the cursor will readily be in register with the end of the scale marking on the stator, and can be quickly moved to that position without the necessity of using undue care or losing time 'in so setting the cursor.

With these and other objects in View, my invention consists in the construction, arrangement, and combination of the various parts of my device whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my claims, and illustrated in the accompanying drawings, wherein:

Figure 1 is an isometric view of a slide rule embodying the present invention;

Figure 2 is a sectional view taken on line 2-2 of Figure 1;

Figure 3 is an end view of the rule illustrated in Figure l, taken from the end thereof nearest the observer;

Figure 4 is an edge view of a portion oi one end of the slide rule;

Figure 5 is a view similar to Figure 4, and il lustrating a different position of the wedge elements making up the slider;

Figure 6 is a view of one of the nat sides' of the slider, with the scale piece removed therefrom;

Figure 12 is a View taken-on line l2-i2 of Figure 10; Y

Figure 13 is an enlarged; sectional view taken on line |3-i3 of Figure 10; and

Figure 14 is a view taken on line iii-i4 of Figure 13.

The slider Referring in detail tothe drawings and particularly Figures 1 to 9 inclusive, the slide rule is composed of a stator I6, a slider I8 and a cursor 2li. The stator i6, as is'usual in slide rules, is made up of a pair of statorelements 22 and 24, which are elongated flat elements, secured together in spaced relation Vby end pieces 2t which are secured across the respective ends of the stator elements Vas by screws or other means for forming a space between the stator elements for the slider. The stator elements 22 and 24 may be made of metal, plastic, or other material, and the opposite faces are provided with the usual scale markings thereon.'

The stator elements 22 and 24 are provided on their outer edge surfaces with longitudinally extending grooveso'r channels 28 and Se for cooperation with tongue elements of the cursor. The groove 2i? is adapted for cooperation with the locking means ofthe cursor referred to above, and which will be explained in detail later and, for this reason, the groove 28 is preferably rectangular in cross-section. vThe groove Se may also be rectangular in' cross-section for purposes of symmetry, although the shape of the latter may be different Vif desired. The stator elements 22 and 24 are also provided with groove elements 32 on their inner Vedge surfaces for cooperation with tongue elements on the slider. Other details of the stator elements may be formed, as desired, for various purposes, the foregoing being designed for purposes of the improvements of the present invention.

The slider I8 is made up of a central core member 34 and side scale pieces 35 and 3S which are provided Y with appropriate scale markings for cooperation with the scale markings on the stator.

The construction of the core member 34 of the slider may be observed more readily from Figures i, 2, and 6, wherein it will be seen that the core member is made up of two separate pieces 4% and 42. The pieces 4U and 42 have cooperating wedge surfaces indicated by the parting line 44, which divides the core member longitudinally of the rule in such'a mannerthat the wedge surfaces of the pieces face each other; each of the wedge pieces 4o and 42 has a large end at one end of theV slider terminating normally substantially flush with the small end of'theother wedge piece.

rZChe wedge piece 4i) of the slider is provided with a central longitudinalv groove 46 which may be cut in from one of the flat surfaces thereof, as for instance the top surface' of Figure G .f This groove may also be seen in Figure 7.v Toward the end of the wedge piece 40 at the left of Figure' is an enlarged opening 48 disposed transversely of the groove 46 and extending through the respective wedge piece. Substantially centrally longitudinally of the wedge piece is a cut-out portion 50 which al-so extends through the wedge piece 4D and is cut downwardly from the wedge surface thereof.

The wedge piece 42 for the most part is symmetrical with the wedge piece 40, having a longitudinal groove 52 centrally of its flat surface Vthereof similar to the groo-ve 46 but wider than the latter, and an opening 54 at the larger end thereof and to the right in Figure 6 similar to the opening 48 at the opposite end of the piece Substantially centrally of the wedge piece 42 is an enlargedcut-out portion 56 extending through the wedge piece 42 and cut from the wedge surface thereof, this opening 56 being of greater dimension longitudinally than the opening 50.

Formed along the outer edge surfaces of the wedge pieces 48 and 42 of the slider are V-shaped tongue elements 58 and 69 extending longitudinally thereof. These tongue elements 58 and 59 are adapted to slide in the groove elements 32 in the inner edges of the stator elements. The tongue element 6B has a cut-out portion 62 centrally thereof in register with a hole 64 extending through the wedge piece 42 and into the cutout portion substantially centrally of the latter.

The wedge portion 42 is provided with cut-out cavities S5 in the wedge surface thereof, disposed parallel with its wedge surface, or'the line 44 between the facing wedge surfaces of the wedge pieces 4e and 42. The wedge piece V4i) is provided with a projection V68 extendinginto each of the cut-out portions 66 at a point in the latter toward the right ofrFigure 6. A compression spring it is positioned in each of the cut-out portions t5 and biased between the respective projection e3 and the end of the cut-out portion farthest from Vthe projection. The springs 7G, therefore, bias the wedge pieces 44 in such a manner as to-separate the wedge pieces,that is, the wedge piece 40 to the right and the wedge piece 42 to the left (Figure 6) spreading the wedge pieces in a direction perpendicular to the length thereof. If desired, thev projections 168 may be adjustable along the wedge surface of the piece 4o and in the cavities 66. y

A shaft 72 is positioned in the grooves or channels 45 and 42 and supports a worm gear 'i4 centrally thereof. The worm gear 14 is thereby disposed in the cut-out portion 5B in the'wedge piece 4e and is secured against rotation on the shaft by means of a set screw'l. Preferably the set screw 'i6 is of the Allen head type, access to which may be gained through the drill hole 64 by means of a small diameter wrench. The worm gear 14 is of such a length to t in the cut-out portion 54 snugly therein, the end portions of the cut-out portion forming stop means for limiting movement of the worm gear and the shaft longitudinally of the slider. Knurled turn wheels 'I8 are secured to the shaft 'l2 and positioned in the cut-out portions 48 and 54. The wheels 'i8 are secured against rotation on the shaft 'i2 'by means of set screws 8B. The'wheels 'I8 are adapted for rotating the shaft 12 and are exposed to access of theuser as will'be explained more fully later.

Each of the wedge pieces 4e and 42 of 'the slider on each side thereof is provided with' lateral extensions 82 having'inclined 'surfaces '84, these surfaces on each side ofthe slider sloping toward each other outwardly of the slider. The surfaces 84, which are disposed on the same side of the slider, form groove elements adapted to receive tongue elements 86 on the scale pieces 36 and 38, by means of which the scale pieces are secured to the core of the slider.

Each of the scale pieces 35 and 38 is provided on its inner surface, and in the respective tongue element 36 with a concave portion indicated generally at 83 (Figures 7 and 8). The concave portions are disposed substantially centrally longitudinally of the scale pieces are adapted to fit over the worm gear 'i4 on the shaft 12. The concave portions 88 are provided with threads 90 to receive the threads of the worm gear 14. The concave portions 86 are longer than the worm gear "I4, and when the scale pieces are secured to the core element of the slider, the worm gear, on turning thereof, is eiective for sliding the scale pieces longitudinally of the slider. The scale pieces and the extensions 82 forming the groove elements, terminate short of the wheels 'I8 as will be observed from Figure l, so that the wheels 'i8 are exposed to easy access by the user.

The means for actuating the locking means of the slider comprises a pair of plates at each end of the slider. Each pair of plates comprises a xed plate 52 and a hinged plate 94, secured on the opposite hat sides of the slider. The fixed plate 92 is secured in each case to the large end of the wedge piece 40 or 42 disposed at that end, by means of screws or other desired means. The hinged plate 94 is provided with an extension 96 which fits in between the arms B8 of a plate |03 secured to the large end of the respective wedge piece, by means oi screws, or other desired means. The plate 94 may be hinged by means of a conpenient pin extending through the arms 98 of the plate |90 and the extension 96. The small end of each wedge piece is free to slide between the small plate and the fixed plate 92. The hinged plate 94 is provided with an extension or foot |02 extending toward the plate 92 and in position for engaging the end surface of the small end oi the respective wedge element. The width of the foot |02 in the direction of the width of the plate is substantially coextensive with the width in that direction of the respective small end of the wedge piece. The hinged plate t4 is biased away from the xed plate 92 by means of a compression spring |04 disposed between the plates. The hinge between the hinged plate 94 and the plate idd may be a conventional hinge having a stop to limit the outward swinging of the plate 94 to a position parallel with the iixed plate S2. The core may be provided with an inclined cut-off portion |05 (Figure 9) to accommodate the downward swinging movement of the portion d6 of the plate 84 when the latter is depressed.

Adjustable stop means |06 is secured to the core member 34 of the slider at each end of the respective scale pieces 36 and 38 and on both sides of the slider' for limiting the longitudinal movement of the scale pieces. rl'he stop means |05 may be a disk, either circular or irregularly shaped, and secured to the core of the slider by means of a screw positioned eccentric to the disk. The screw may be loosened and the disk positioned in various positions of angular adjustment, thereby acting as a cam having diierent surfaces engageable by the scale piece for varying the limit of movement of the latter. The screws securing the disks |06 are positioned offset with respectto the grooves 46 and 52 so that the screws 6 can be run into the core of the slider a sumcient extent to be properly secured therein.

Use cmd operation of the slider The groove elements formed by the inclined surfaces 84 in the wedge elements 40 and 42, and the cooperating tongue elements 86 in the scale pieces 36 and 38, can have such an inclination that only a slight extent of wedging movement is necessary for inserting the scale pieces and securing them in place. In assembling the slider, the wedge elements are placed together with their wedging surfaces interengaging and slid relative to one another so that the groove elemen-ts thereotformed by the inclined surfaces 84, are spread wide enough for the insertion of the tongue elements 6 on the scale pieces. One scale piece is then put in place by inserting the tongue element 86 thereof into the groove element of the wedge pieces. The iirst scale piece may be, for example, 3d which is to ce placed on the underside of the slider as viewed in Figure 6. Then the worm gear lll is inserted in position in the cut-out portion E@ and a small diameter wrench inserted through the hole 64 and into the set screw 16. The next step is to place the compression springs 'I0 in the cut-out portions 6d as illustrated in Figure 6. Then the scale piece 36 is placed on top of the slider and the two wedge pieces slid so that the groove elements in the wedge pieces are brought into engagement with the tongue elements on the scale pieces. rEhe initial movement of sliding the wedge pieces may have moved the grooves 45 and 52 out of alignment but, after the two scale pieces are placed on the core, the Wedge pieces are brought back to the positions where the grooves 46 and 52 are in alignment. The wheels 13 are then inserted into the cut-out portions 48 and d4. Then the shaft i2 is inserted into the groove 52 which opens out of the end of the wedge piece and inserted through the respective wheel 78, the worm gear le, the groove 46, and finally through the wheel 'it at the far end. The wrench previously inserted through the hole 64 and into the set screw 'i6 is utilized for tightening the worm gear 'i4 onto the shaft. Then the set screws 80 in the wheels 'i8 are tightened. After these steps have'been completed, the plates 92 and 94 are secured on the large ends of the wedge pieces 40 and 42. Thereafter, the stop means |06 can be secured in place.

The thickness through the slider and scale pieces S5 and 3S is substantially the same thickness as through the plates 92 and 94, this thickness being also the thickness of the stator pieces 22 and 24 so that the slider can he easily slid through the end pieces 26. Ii desired, the end pieces 2G can be provided with arcuate cut-out portions Hi8 to accommodate wheels 18 of a diameter greater than the thickness of the assembled slider.

The compression springs 'i6 in the cut-out portions to normally bias the wedge pieces 40 and 42 in directions such that the wedge surfaces thereof force the wedge elements into engagement with the stator elements 22 and 24. The extent of movement sideways into engagement with the stator eiements need be practically only an infinitesimal amount for purposes of friction locking the slider with the stator.

When the user wishes to slide the slider, he merely presses together on the plates 92 and 94 at either end of the slider, and the relative movement together of these plates forces the wedge elemente 40 and 42 in the direction opposite to that biased by the springs lll, thereby releasing the friction engagement between the wedge pieces and the stator elements and enabling the slider to be easily slid through the rule. This relative movement is indicated to an exaggerated degree in Figure 5. The plates 92 and Sie being posi tioned at both ends of the slider, the use;1 can quickly release the locliing means of the .slider and, after the slider is moved to the approximate position desired, he releases the plates and the slider is eiectively locked lthe position set. After the approximate position of the slider is set'by the user, and the scale marking on the slider is not in exact re ster with the intended marking on the stato; element, the ruser merely turns one of the wheels ld. This rotation of the wheels le. acting through the shaft T2. rotates the worm gear which, being .secured against longitudinal movement in the slider by means of its close nt fm the cut-out portion Sil, adjusts the scale pieces longitudinally along the slider. Rotation of the worin gear acting on the threads 9S in the scale pieces produces micrometric movements of the scale pieces by means of which the user can produce exact adjustment of the scale pieces.

lThe scale pieces it Vand 38 may be of metal, as actually produced Vin many cases; and, when made of metal, the threads Sii can be cut directly into the vmaterial forming the scale pieces, eliminating the necessity for insertion of a hard surface bearing material.

The cursor The cursor 253 :referred to generally above .cornl prises a pair of'transparent side plates H as is usual in cursors, secured together by a spacer .element i l2 at one end engaging the stator element The spacer lis provided with a 'tongue velement Hel which is received in v'and slides in the groove in the stator element 2d. The opposite ends of the side plates Il@ contain .the locking means and micrometric movement means for controlling the movements of the cursor. This mechanism is referred to generally at 116.

Referring particularly to Figures 10 vto 14, this mechanism includes a lever H8 pivoted-at |20 'in a .pin supported by the side plates it. The lever lil! Vhas an upwardly extending short portion |l2| which extends up into `the groove 23 in the stator element 22. The lever lit also includes along por-tion .22 which extends horizontally along vthe stator element between the side plates Iand .has a terminal portion 'i2-'l extending slightly beyor-id the side plates lit. A pin li is ysupported the lever 'i i8 at a point substantially centralof the cursor longitudinally of the rule, and kthis pin '|25 supports a pair of rollers |23, one on each Vside of the lever. The pin |26 is -xedly secured in the 'lever and outer ends 'thereof extend through slots |36 formed inthe rollers L28 of an extent vertically slightly larger than the diameter of the pin |25.

Spacers is? are positioned on either side of A.the lever Esc and extend from the bottom ledge of Y vrollers iii-e thereinI :thelower end of the-cut-out portions being rounded to conform to the shape of the rollers. Secured to and between the side spacers |32 is another member |38 disposed above the lever |2i `and extending from the side of the cursor having the extension i2@ of the lever to a point slightly short oi the upstanding leg portion ji2| or the lever. This member |33 is positioned in register with the undersurface of the groove 28 in the stator element 22. A compression spring |43 is biased between member |33 and the lever i I3, being secured in place in sockets therein and effective for biasing the leg portion |22 of the lever H8 downwardly. A lpair of wedge elements |132 and |5263 are positioned above and secured to the member |38 in position to be received in the groove 28 in the stator. The wedge elements U andV Idil are divided by a line ist (Figure 1.2) forming interengaging wedge surfaces. The wedge element e2 may be a part of the member |38 or rit may `e a separate piece and 'secured thereto. The wedge element ld is separate from the element les and is secured thereto by'rneans o a screw |-l3 threaded through an elongated slot ld which is disposed parallel with the Adividing Aline i535. The slot iEv, as ilrlustre-tad in Figures 12 and 14, is exaggerated in extent, since the slot need be only slightly larger than the diameter of the screw iS. The wedge member 'lill is adapted to have relative motion with respect to the wedge piece |42 as will be explained later in detail, and the slot ld is adapted to slide over the screw Hi8 in such sliding movements. The wedge piece |42 is provided with a cut-out portion or cavity in its wedge surface ,and is adapted to receive .adjacent one end thereof a projection |53 secured to the wedge surface of the wedge piece idd. The cavity |52 may be disposed intermediate vthe upper and lower surfaces of the wedge members (Figure 14), or it may be cut in the top surface of the wedge .member as viewed in Figure i2. A compression spring 55e is interposed in the cavity |52 between the projection |53 and the end of the cavity .farthest therefrom, and is effective for reacting between the wedge pieces ybiasing the wedge member |44 to the right (acting through the projection |53) and the wedge member lil? to the left (Figure 12), or in directions contr-acting the 'two elements away from the side walls or the groove 28 in the stator element.

Stop means |56 are provided in the groove 23 to .adjustably limit the extent of movement of the cursor. .Each stop means |56 may be an Vinsert ,lling the groove and is provided with an .adjustable set screw |58.

vUse vund operation of' the cursor 'in any undisturbed position oi the cursor 2t, the compression spring itil biases the long leg 22 of the lever H8 downwardly, rotating the Ilever .i I8 counter-clockwise and bringing the short `leg 12| thereof into engagement with the wedge .element ldd. This action biases the wedge element Ide tothe left as viewed in Figure '12, relatively sliding the wedge elements |52 and ldd together and effectively spreading them sideways into engagement with the side surfaces of the groove .28 in the stator element. The compression spring .Idil is strong enough to overcome the counteracting compression spring |56, vthus lock-ing the cursor in the particular position set on the slide rule.

When the user desires to slide the cursor along the rule, The presses the lever ||8 by means of the extension 12# which swings `the short leg |2| of the lever outwardly from and releases the pressure against the wedge element |44. Thereafter, the compression spring |54 becomes effective for causing relative sliding movement between the wedge elements longitudinally of the groovel 28 whereby the wedge elements are contracted transversely, bringing them out of frictional engagement with the side surfaces of the groove 28. The cursor can then be easily slid along the rule and, when it is brought to the approximate position desired, the lever |I8 is released and the cursor is locked in the position set.

The means for producing micrometric movements of the cursor consists of the roller means 25. The user presses on the rollers |28 which are normally out of engagement with the edge surface or" the stator element 22. The rollers, when pressed against the stator, come into engagement with the latter and, at the same time, the pin l forces the lever H8 clockwise and releases the pressure exerted against the wedge element i644. The locking means is thus released and the user can roll the rollers along the stator element, the cursor then being moved along the rule at a reduced rate of movement.

The set screws |58 may be adjusted through the inserts |56 in one direction or the other longitudinally of the grooves to adjustably limit the extent of movement of the cursor to position the index line thereof over the end mark of the scale markings on the rule. Such stop means are shown in the groove 28 but, if desired, they may be provided in the groove 30 so that the stop means does not interfere with the proper operation of the short arm |2I of the lever H8.

If the diameter of the wheel 18 is such as to extend beyond the dimensions of the scale pieces 36 and 38 in theslider, the side plates of the cursor may be provided with arcuate cut-out portions |60.

While I have herein shown and described a preferred embodiment of my invention, manifestly it is susceptible of modication and rearrangement of the parts without departing from the spirit and scope thereof. I do not therefore, wish to be understood as limiting my invention to the precise form herein disclosed, except as I may be so limited by the appended claims.

I claim as my invention:

l. In a slide rule having a pair of stator elements and a slider slidable therebetween, said slider comprising a core member formed of separable parts, said parts being engageable with said stator elements, means biasing said parts into engagement with said stator elements, releasing means carried by the slider and adapted to move said parts out of engagement with said stator elements, and a scale piece carried on each side of the core member.

2. In a slide rule having a pair of stator elements and a slider slidable therebetween, said slider comprising a core member formed of sepa- .rable parts, said parts being engageable with said stator elements, means biasing said parts into engagement with said stator elements, releasing means carried by one of said parts and engageable with the other part for moving said parts out of engagement with the respective stator elements, and a scale piece carried on each side of said core member.

3. In a slide rule having a pair of stator elements and a slider slidable therebetween, said slider comprising a core member and a scale piece on each side thereof, said core member being formed of separable, oppositely disposed,

wedge-shaped parts extending longitudinally the length of the slider, each of said parts being engageable with one of said stator elements, said parts having interengaging inclined surfaces, biasing means interacting betwen said parts and biasing the parts in opposite directions longitudinally of the rule causing said inclined surfaces to force the parts outwardly into engagement with the respective stator elements, and releasing means carried by the slider adapted to move said parts in directions respectively opposite to the movements caused by said biasing means.

4. In a slide rule having a pair of stator elements and a slider slidable therebetween, said slider comprising a core member and a scale piece on each side thereof said core member being formed of separable oppositely disposed, wedgeshaped parts extending longitudinally the length of the slider, each of said parts being engageable with one of said stator elements, said parts having interengaging inclined surfaces, biasing means interacting between said parts and biasing the parts in opposite directions longitudinally of the rule causing said inclined surfaces to force the parts outwardly into engagement with the respective stator elements, and releasing means carried by the large end of each wedge-shaped part, each releasing means being operable to en gage the adjacent small end of the other wedgeshaped part and interact between the two parts for moving the parts in directions respectively opposite to the movements caused by said biasing means, said releasing means being operable independently of each other.

5. In a slide rule having a pair of stator elements and a slider slidable therebetween, said slider comprising a core member and a scale piece on each side thereof, said core member being formed of separable, oppositely disposed, wedge shaped parts extending longitudinally the length of the slider, each of said parts being engageable with one of said stator elements, said parts havn ing interengaging inclined surfaces, biasing means interacting between said parts and biasing the parts in opposite directions longitudinally of the rule causing said inclined surfaces to force the parts outwardly into engagement with the respective stator elements, and releasing means carried by the large end of each wedge-shaped part, each releasing means comprising a pair of spaced plates extending longitudinally outwardly from the end of the slider and within the connes of the longitudinal projection thereof, one of said plates being rigidly fixed to said wedgeshaped part and the other plate being hinged thereto, said hinged plate having a lateral extension engageable with the adjacent small end of the other wedge-shaped part, said hinged plate being swingable toward said fixed plate whereby said lateral extension bears against the other wedge-shaped part and the hinged plate interacts between the two wedge-shaped parts and moves the latter in directions respectively opposite to the movements caused by said biasing means.

6. A slide rule comprising a pair of stator elements and a slider slidable therebetween, said slider having portions expandible and contractible toward and away from said stator elements, biasing means operable to expand said portions, means operable to contract said portions, and a scale piece on each side of the core member, said scale pieces and core member having interlocking dovetail tongue and groove elements for re taining the scale pieces on the core member, said Il scale pieces being movable longitudinally on said core member.

7. In a slide rule having a pair of stator elements and a slider slidable therebetween, said slider comprising a core member formed of separable parts, said parts being engageable with said stator elements, means biasing said parts into engagement with said stator elements, releasing means carried by the slider and adapted to move said parts out of engagement with said stator elements, and a scale piece on each side of said core member, said scale pieces and the parts of said core member having interlocking dovetail tongue and groove elements for retaining said scale pieces on said core member, the extent of inclination of the interengaging inclined surfaces of said tongue and groove elements being greater than the extent of movement of said parts toward and from said stator elements.

8. In a slide rule having a pair of stator elements and a slider slidable therebetween, said slider comprising a core member, a scale piece carried on each side of said core member, said scale pieces being movable longitudinally of said core member, a shaft rotatably mounted in said core member, means secured to said shaft eX- tending out of said core member for rotation of said shaft, and means on said shaft and scale pieces cooperable on rotation of said shaft for micrometer adjustment of said scale pieces longitudinally of said core member.

9. In a slide rule having a pair of stator elements and a cursor slidable thereover, said cursor having a pair of Wedge shape portions adapted to engage one of said stator elements, said Wedge shape portions having interengaging' inclined surfaces and adapted to have relative sliding movement for expansion and contraction thereof, biasing means operable for contracting said Wedge shape portions, biasing means operable for expanding said Wedge shape portions, and means for inactivating said last-named biasing means.

10. In a slide rule having a pair of stator elements and a cursor slidable thereover, said cursor having a pair of Wedge shape portions having interengaging inclined surfaces, one of said Wedge shape portions being slidable with respect to the other, said wedge shape portions, on relative sliding thereof, being expandible and contractible, one of said Wedge shape portions being adapted to engage one of said stator elements, means biasing said slidable Wedge shape portion in contracting direction, means biasing said slidable Wedge shape portion in expanding direction, and means for inactivating said last-named biasing means.

ARTHUR F. ECKEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 651,142 Keuffel June 5, 1900 879,237 Baumbach et al. Feb. 18, 1908 1,000,562 Steber Aug. 15, 1911 1,572,497 McCarter Feb. 9, 1926 1,605,922 Cook Nov. 9, 1926 1,904,474 Keuiel Apr. 18, 1933 2,143,559 Keuiel Jan. 10, 1939 FOREIGN PATENTS Number Country Date 232,037 Great Britain Apr. 16, 1925 482,659 Germany Sept. 19, 1929 577,358 France June 3, 1924 

